DE1081505B - Transistor switch for quick demagnetization of inductive power consumers - Google Patents

Description

The use of transistors as electronic switches in the circuit is permitted by the maximum Reverse voltage limited. When this peak reverse voltage is exceeded, the transistor destroyed.

For example, for rapid demagnetization of an inductance, the current flow must be interrupted Switching element as high a voltage as possible are permitted, since the compensation process is so the faster the higher the cut-off voltage peak. This also applies when the balancing process is not carried out via linear, but via voltage-dependent resistors.

Since the permissible reverse voltage of the transistors in switching arrangements for blocking the applied If the mains voltage is largely used up, an additional voltage application can no longer be permitted will.

The invention relates to a transistor switch for rapidly demagnetizing inductive power consumers with an arbitrarily controllable switching device serving to switch the supply voltage, which consists of one or more transistors and in series with one or more transistors is connected and consists in that the additional transistors connected in series only then are claimed in the reverse direction if the rectifier 5, the resistors 7 and 8, etc. a Equalizing current flows, and that the additional transistors only through part of the induction voltage are acted upon during the switch-off process and to limit the voltage of each of these transistors a resistor is connected in parallel.

A circuit example according to the invention is shown in the figure, with the aid of which the mode of operation is also explained. The three power transistors 1, 2 and 3 are connected in series. The transistor 1 is switched via a flip-flop 14, which is controlled by the signal arriving at 15. The transistor 1 represents the actual switching transistor, the permissible reverse voltage of which must be greater than the applied direct voltage U.

Transistors 2 and 3 allow a switch-off voltage peak during the equalization process, which would destroy a single transistor. If the transistor 1 becomes conductive, the emitter potential of the transistor 2 becomes positive and it flows in Control current via the base and the resistor 12, so that the transistor 2 is controlled and conductive, so that the emitter of transistor 3 also becomes positive. A base current flows through the transistor 3 via the Resistor 11 and the rectifier 6, so that the transistor 3 is also conductive and the operating current via the resistor 16 and the coil 4 flows.

for quick demagnetization

inductive power consumer

Applicant:

LICENTIA Patent -Verwaltungs -G.m.b.H., Frankfurt / M., Theodor-Stern-Kai 1

Walter Stübchen, Frankfurt / M.,
has been named as the inventor

If the transistor 1 is blocked, the operating current initially flows through the inductance 4 via the rectifier 5. Due to the voltage drop across the rectifier 5, the base potential of the transistor 2 becomes positive compared to the emitter potential, so that the transistor 2 is blocked. At this moment, the voltage U is present at the transistor 1, increased by the voltage drop across the rectifier 5.

When the transistor 2 is blocked, the equalizing current flows via the resistors 7 and 8. The base of the transistor 3 is connected via the resistor 10 between the resistors 7 and 8, so that the base of the transistor 3 is positive with respect to the emitter and the transistor 3 is blocked. If all the transistors are blocked, the equalizing current flows back to the inductance via the rectifier 5, via the resistors 7, 8, 9 placed parallel to the additional transistors and via the resistor 16.

The voltages dropped across transistors 2 and 3 are limited by the parallel resistors. For transistor 2, the base voltage is limited during the equalization process by the voltage drop across rectifier 5, while the base voltage at transistor 3 is limited by the voltage divider circuit of resistors 7 and 8. The rectifier 6, which is stressed in the reverse direction during the switch-off process, prevents the potential - U from reaching the base of the transistor 3 and thus the potential of the transistor 3 from becoming impermissibly positive with respect to the emitter.

In principle, the circuit can be made up of further transistors, which work in the same way as transistor 3 are switched, for any high switch-off peak

O09 50972-78

tensions are designed. The parallel resistors 7, 8 and 9, through which the equalizing current flows, can be replaced by non-linear resistors.

The circuit example described in the figure is designed for pnp transistors. Through appropriate Polarity reversal can also be carried out for npn transistors or for both together will.

Claims (5)

Claims: 10 1. Transistor switch for quick demagnetization of inductive power consumers with a arbitrarily controllable, for switching the supply voltage serving switching device, the one or more transistors and connected in series with one or more transistors is, characterized in that the transistors additionally connected in series only are then claimed in the reverse direction, if via the rectifier (5), the resistors (7 and 8) etc. an equalizing current flows, and that the additional transistors only through one Part of the induction voltage are applied during the switch-off process and for the limitation the voltage of each of these transistors is connected in parallel with a resistor. 2. Transistor switch according to claim 1, characterized in that the individual switching transistors (2, 3) resistors (7, 8, 9) placed in parallel are non-linear resistors. 3. Transistor switch according to claim 1 and / or 2, characterized in that the base voltage the switching transistors (2, 3) via a voltage divider from the upstream transistor is tapped. 4. Transistor switch according to claim 3, characterized in that the base voltages of the Switching transistors (2, 3) limited by diodes (5_, 6) will. 5. Transistor switch according to claim 1 and 3, characterized in that a diode (6) in Series to the resistor (11) is placed, is claimed in the reverse direction during the shutdown process and prevents the base reverse voltage from becoming unacceptably high. Considered publications:
German interpretative document No. 1 020 673. 1 sheet of drawings ■ © 009 509/278 5.60